Among the great variety of lactone derivatives which have found sofar an industrial application in the field of perfumery, there appear to be numerous .gamma.- and .delta.-lactones whose odorous properties could be defined as being of fatty, coco-nut, flowery and fruity type. Some lactones are further characterized by an odour reminiscent of vegetable, celery in particular, or lovage [see: S. Arctander, Perfume and Flavor Chemicals, Montclair U.S.A. (1969), Secs. 416, 828, 829, 1102, 1103, 1504, 1590, 1648 etc.]. Specific examples of such derivatives are indicated for instance in U.S. Pat. No. 3,380,457 which document describes the use of lactones having generic formula ##STR1## comprising a single or a double bond in the position indicated by the dotted lines, and wherein each of substituents R.sup.1, R.sup.2 and R.sup.3 represents a hydrogen atom or an alkyl radical, as flavouring agents for tobacco products. The following compounds have been disclosed in the cited U.S. patent as being derivatives of special interest: ##STR2## 3-isopropyl-.delta.-valerolactone; ##STR3## .delta.-lactone of 5-hydroxy-3-isopropyl-pent-2-enoic acid; ##STR4## p-methyl-.delta.-valerolactone.
U.S. Pat. No. 3,996,170 describes the use as perfuming agents of lactones of formula ##STR5## wherein R.sup.1 represents a methyl radical or a hydrogen atom, and R.sup.2 represents an alkyl group containing 3 to 5 carbon atoms. Said lactones of formula (II) possess notes as varied as sweet, floral, herbal, green, celery-like, coconut, coumarin, lovage-like, foenugreek, tagette.
When we have tried to repeat the process for the preparation of 6-n-butyl-alpha-pyrone--the compound of formula (II) wherein R.sup.1 .dbd.H and R.sup.2 .dbd.n-butyl--in accordance with the disclosure of cited U.S. Pat. No. 3,996,170, we have noticed that the obtained substance polymerized rapidly at room temperature, it became yellow and its smell gradually changed and denaturated.
We have now discovered that two compounds of analogous structure viz. 6-ethyl- and 6-n-butyl-5,6-dihydro-2H-pyran-2-one, possessed very useful odorous properties and consequently could be advantageously used in the perfume industry. The two compounds cited above presented, in contradistinction to the mentioned 6-n-butyl-alpha-pyrone, a constant and homogeneous odorous note; moreover, the lactonic-celery character of 6-n-butyl-alpha-pyrone is practically absent in the two compounds of the invention, whose character is more spicy and fruity. Owing to their properties, 6-ethyl- and 6-n-butyl-5,6-dihydro-2H-pyran-2-one find a particular application in the compounding of composition of fougere, chypre, lavender or even fruity type.